Not much there in your article. So "80-95 percent of coral colonies were bleached in some reef areas". So what? Did the warm ocean cause it? Are the oceans warmer than past events? Unlikely since these are strictly local phenomena, and the satellite monitoring started in 1997. From the NOAA link in your article:
The bleaching events reported prior to the 1980s were generally attributed to localized phenomena such as major storm events, severe tidal exposures, sedimentation, rapid salinity changes, pollution, or thermal shock. The events since 1980 have not been so easily explained. http://www.coralreefwatch.noaa.gov/satellite/index.html IOW, before the 1990's it wasn't fashionable to blame everything on man-made global warming and now it is. Here's a more balanced perspective: Fears fade on Barrier Reef bleaching disaster
And the article you link to concludes:
Numerous laboratory studies have shown a direct relationship between bleaching and water temperature stress. Elevated water temperatures have been implicated in the majority of the major bleaching events of the 1980s and 1990s.